The invention relates to the generation of electricity or mechanical power from renewable sources such as wind and/or water currents. Presently, wind mills and tidal current power generators consist of a single turbine that rotates around either a horizontal or vertical axis. The rotating turbine sets in motion a drive train that is connected to an electrical generator. The generator converts the wind and/or water current into electrical power, and the electrical power is transmitted to the electrical grid and distributed.
Horizontal axis turbines dominate the field of wind harvesting; however, to maximize the amount of energy generated and make said turbines cost-effective, these turbines require a large diameter. Due to their size, however, horizontal axis turbines have significant drawbacks, including: 1) the need for a strong structure to support the turbine; 2) difficulty transferring the turbine and support structure to the installation site; 3) a large drive train is required to transfer power from the rotor to the generator; 4) an assistive device such as an electric yaw is needed to keep the rotor pointed head-on into the wind; 5) the rotor blades are exposed to gale-force winds, wind shears, high-speed winds, turbulence, and irregular wind flow and need special mechanisms to protect them from more extreme conditions; and 6) the individual components of the turbine and support structure are expensive to fabricate, test, and change out when needed. These drawbacks combine to result in windmills and wind farms that are expensive to develop and maintain.
To partially eliminate the drawbacks of the horizontal axis turbine, vertical axis turbines with short, light-weight towers have been designed. However, these towers become unstable above a certain height and require additional support at the top of the rotors to maintain stability and proper rotation. This instability at higher altitudes results in the rotors being placed nearer to the ground. The closeness of the rotors and generators to the ground makes repairs easier and cheaper, but the turbine has difficulty self-starting and generates less electricity because wind speeds are slower near the ground.
To solve the issues associated with horizontal and vertical axis turbines, Selsam developed a serpentine wind turbine consisting of multiple small rotors installed on a flexible turbine driveshaft (U.S. Pat. No. 6,616,402 B2). However, the invention's adjacent aft rotors are positioned partially in the wind shade of the fore rotors, an alignment that greatly reduces system's efficiency. To overcome this problem, Selsam then designed a multi-rotor wind turbine that uses a generator as a counterweight (U.S. Pat. No. 7,063,501) and a side-furling co-axial multi-rotor wind turbine (U.S. Pat. No. 7,063,501). Both inventions lower the amount of wind shading that occurs, but neither eliminates it. Additionally, the rotors of the inventions are on an identical plane, which limits the amount of wind that can be converted into energy. Finally, the inventions are specifically designed to be used in wind currents and no means are provided to make said inventions effective in other fluid environments.